There are plural linear motors, servomotors or stepping motors used in various carrying devices, moving parts of industrial robots and various tables used in machine tools. As drivers of these motors drive them independently on an axis basis, specific parameters are set for the respective drive axes. In addition, as for each of the drive axes, its driving method needs to be changed in accordance with the use conditions, the parameters need to be set appropriately for the respective drive axes in accordance with the use conditions.
The multi-axis driver holds particular parameters for respective drive axes and has a function to control motors provided for respective drive axes independently based on the parameters, programs held on the drive-axis basis and the like.
Here, setting or change of axis basis parameters or, for example, parameters regarding motor rotation is generally performed by connecting the multi-axis driver to an external device and inputting desired parameter values with use of the external device. Such an external device may be a special input device, a general-purpose personal computer or the like. Here, the driving system such as an actuator, the multi-axis driver for controlling the driving system and an external device for setting the parameters of the multi-axis driver make up a so-called multi-axis drive control system.
As a conventional multi-axis drive control system needs to output driving signals to plural motors, respectively, as disclosed in the patent document 1, a drive control board is provided for each drive axis and such drive control boards are built on the substrate.
Thus, the conventional multi-axis drive control system is configured to have the drive control boards having driver circuits with microcomputers for respective axes (respective motors to control) for control of the axes and to control operation amounts, the operation orders of motors on a drive-axis basis and the like.
Further, the drive control board needs an interface to receive commands issued from an external device and it is configured to be able to, for example, change, write and store parameters of the driver for controlling the motor via the interface by the external device. Furthermore, setting of monitor display method, setting of the communication speed, setting of temporary simple job operation and check of the operation and the like are performed with use of the external device. Interface communication standards for such external input includes serial communication, parallel communication, LAN and the like. However, many personal computers use RS232C external interface as external input device.
As described above, in the conventional multi-axis drive control technique in which, for example, N motors are used to drive the N axes, the control needs N drive control boards, and also needs RS232C ports as external interfaces for respective drive control boards. Here, as RS232C is one-to-one communication standards, multi connection is difficult in terms of hardware. Besides, as the standards are of one-to-one communication only, this RS232C communication protocol is also configured based on one-to-one communication.
The patent document 2 discloses a technique of creating a multi-dropped network that allows multi connection in the RS232C one-to-one communication hardware and communication protocol. As disclosed in the patent document 2, the network is constructed in optical communications having plural automatic dispensers (1A to 1C) by interposing an RS232C/RS485 converter having a software-like switching function to the hardware based on one-to-many or many-to-many interface standards (RS485) in the network having the hardware based on the one-to-one interface standards (RS232C) and the communication protocol and achieving multi-dropped connection.
However, although the RS485 allows connection of plural modules having unique IDs thereunder, there are some problems in view of two-way communication. For example, the modules are configured to simultaneously receive data sent via the RS485 but to reply to the self-addressed data only when a communication line for transmission is available. Therefore, there occur problems that the response data comes into collision with other data and the response to the external device is delayed. Further, as communication from the modules to the external device is always available, they are problematically susceptible to external noise.
In a recent industrial machine tool, highly-accurate positioning, for example, of 1 micrometer or less and high-speed control are required. For such highly-accurate and high-speed multi-axis drive control, displacement of stop position, malfunction due to the external noise and the like are critical problems in the multi-axis drive control system.
Further, when the axes to control are increased in number, the driving portion (driver) is upsized and wiring between the driver and each motor becomes complicated. Furthermore, in the machine and equipment that make greater use of multi-axis drive control, the prices of a board and an external interface provided for each axis directly brings about a cost increase of the drive control system.    [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-287476    [Patent Document 2] Japanese Patent Application Laid-Open No. 8-161604